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浅埋中厚煤层沿空留巷底板变形力学分析及底鼓控制技术

Mechanical analysis of floor deformation and floor heave control technology for gob-side entry retaining in medium thick coal seam with shallow cover depth

  • 摘要: 沿空留巷技术对提高煤炭采出率、改善巷道应力环境及保障矿井安全、高效有重要意义。为了解决浅埋煤层沿空留巷底鼓变形的问题,以乌兰木伦煤矿12407和12408综采工作面为工程背景,基于顶板载荷条带分割法引入等效载荷概念,建立沿空留巷底板等效载荷分布模型,进行沿空留巷底板力学分析并计算出巷道底板的最大底鼓量,采用FLAC3D数值计算方法分析沿空留巷底鼓变形主控因素,数值模拟结果显示:巷旁充填体与隔离煤柱的强度差异性导致巷道底板非对称变形,同时在超前高应力和高强度支护的复合作用下,底板成为围岩承载系统中的薄弱环节最终发生破坏,基于上述理论分析、数值模拟及现场工程实践提出浅埋煤层沿空留巷底鼓控制技术。结果表明:沿空留巷严重底鼓主要是由于工作面推进后超前段煤帮塑性区煤体和巷旁支护体处于高应力作用下,致使底板岩层发生高应力剪切破坏和拉伸破坏;通过优化支护方案,防止工作面推进后顶板无法及时垮落造成悬顶,可有效减小留巷底鼓变形,并提出了巷旁充填体迎山角浇筑设计,优化巷旁充填体参数与底板岩层强度匹配等沿空留巷底鼓防治措施,从减小高应力区应力集中、缓解巷道底板卸压变形和提高底板岩层强度3方面控制沿空留巷底鼓量。现场工程实践表明,上述方法对沿空留巷底鼓作用有良好改善,保障了沿空留巷安全,实现矿山无煤柱的安全经济开采。

     

    Abstract: Gob-side entry retaining technology is of great significance to improve coal recovery rate, improve roadway stress environment and ensure mine safety and efficiency. In order to solve the problem of floor heave deformation of gob-side entry retaining in shallow coal seam, based on the engineering background of 12407 and 12408 fully mechanized mining face in Wulanmulun Coal Mine, the concept of equivalent load is introduced based on the roof load strip segmentation method, and the equivalent load distribution model of gob-side entry retaining floor is established. The mechanical analysis of gob-side entry retaining floor is carried out and the maximum floor heave of roadway floor is calculated. FLAC3D numerical calculation method is used to analyze the main control factors of floor heave deformation of gob-side entry retaining. The numerical simulation results show that the strength difference between roadside filling body and isolated coal pillar leads to asymmetric deformation of roadway floor, and under the combined action of advanced high stress and high strength support. The floor becomes the weak link in the bearing system of surrounding rock and finally fails. Based on the above theoretical analysis, numerical simulation and field engineering practice, the floor heave control technology of gob-side entry retaining in shallow coal seam is proposed. The conclusions indicate that the serious floor heave of gob-side entry retaining is mainly due to the high stress shear failure and tensile failure of the floor strata caused by the high stress of the coal body in the plastic zone of the advance section and the roadside support body after the working face advancing. By optimizing the support scheme, the roof can be prevented from falling in time after the working face is advanced, which can effectively reduce the deformation of the floor heave of the retaining roadway. The design of the filling body at the mountain corner is proposed, and the matching of the filling body parameters and the strength of the floor rock layer is optimized. The prevention and control measures of the floor heave of the gob-side entry retaining are to control the floor heave of the gob-side entry retaining from three aspects : reducing the stress concentration in the high stress area, alleviating the pressure relief deformation of the roadway floor and improving the strength of the floor rock layer. The field engineering practice shows that the above method has a good improvement on the floor heave effect of the gob-side entry retaining, ensures the safety of the gob-side entry retaining, and realizes the safe and economic mining of the mine without coal pillar.

     

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